Celluloid is regarded as the first thermoplastic material, a material created by Alexander Parkes in 1862, by mixing cellulose nitrate with camphor to produce a hard, flexible material which he trade named Parkesine. Today, celluloid is generally considered to be a class of materials created from nitrocellulose and camphor, which is highly flammable. Typically, celluloid is composed of 70 to 80 parts nitrocellulose, nitrated to 11% nitrogen, and about 30 parts camphor, which acts as a plasticizer for the nitrocellulose, plus small parts dyes, stabilizers and other ingredients to increase stability and reduce flammability.
Commercial manufacture of celluloid typically involves mixing nitrocellulose and camphor in the presence of solvents, such as ethanol and acetone. A common celluloid manufacturing process, known as “blocking,” involves mixing the nitrocellulose, camphor, and other ingredients, followed by straining, roll milling and “hiding”. A selected number of “hides” are then blocked at a desired pressure and temperature into a fused block, which is then sliced into sheets at desirable thickness after a conditioning period. Alternatively, celluloid can be manufactured by “film casting,” which involves mixing nitrocellulose, camphor, and other ingredients, and subsequently casting, and drying, the mixture into film of a desired thickness.
As stated above, other than nitrocellulose and camphor, celluloid may contain a number of other ingredients, or additives, such as dyes and fillers for various applications. Common applications for celluloid, today, include guitar picks, ping-pong balls, and some writing and musical instruments.
It is known that celluloid can easily be formed into relative rigid structures of relatively complex geometries and is useful for casings for explosives, or flares, or munitions; however, the various combustible applications experience burn residue issues, as well as, other issues of mechanical strength and embrittlement, especially at low temperatures. Of these issues, burn residue issues are the most problematic; especially when, celluloid is used as the material of construction for combustible increment containers for pyrotechnic or military mortars (aka mortar increment charges or MICs), and in other artillery propulsion systems—burn residue can obstruct launch tubes of the various projectile/artillery systems. Any such obstruction, within a launch tube, can lead to misfires or hang fires, which could result in an untimely detonation of the projectile, with significant potential for injury or death to the crew.
U.S. patent application Ser. Nos. 12/977,374 and 12/483,420, disclosure foamed celluloid, a fast burning material that is almost completely flammable—such that it is essentially residue free—thereby, among other things, avoiding the above detailed problem of obstructions within launch tubes. Further, casings for explosives, or flares, or munitions, or the like manufactured of foamed celluloid do not suffer from the mechanical strength and embrittlement issues that such products manufactured of celluloid suffer from at low temperatures. However, there is a need in the art for an economically process to mass produce such foamed celluloid.